Question

1. the amount of overload that can be handled safely is called the ____a. safety limitb. maximum overloadc. trip settingd. service factor21. __ protection is sized according to the motors service factor.a. fanb. stallc. locked-rotord. run22. a motor with a service factor of 1.1 can withstand an overload condition of __%.a. 600b. 125c. 25d. 1023. the most common cause of motor failure is __a. locked rotorb. mechanical overloadc. excessive bearing weard. current surge24. a worn bearing in a motor may be indicated by __.a. a loud roarb. excessive vibrationc. excessive heatd. all of the above.25. when a three-phase motor is running and one of the three fuses blows, you will have a(n) __ condition.a. single-phasingb. under-currentc. two-fused. dual-phasing26. a ____ ammeter can be used to compare each of the three-phase conductors to see if they have equal current.a. volt-ohmb. direct-currentc. clamp-ond. low-current

Explanation:

1. The service factor defines the safe overload capacity of a motor.
2. Run protection is sized based on the motor's service factor to handle safe overloads.
3. A service factor of 1.1 means the motor can handle 10% overload (1.1 - 1 = 0.1, or 10%).
4. Excessive bearing wear is the most prevalent cause of motor failure due to constant friction.
5. Worn bearings create noise, vibration, and increased heat from friction.
6. When one fuse blows in a three-phase motor, it operates on two phases, called single-phasing.
7. A clamp-on ammeter allows non-invasive measurement of current in each three-phase conductor to check for equality.

Answer:

1. D. service factor
2. D. Run
3. D. 10
4. C. excessive bearing wear
5. D. All of the above.
6. A. single-phasing
7. C. clamp-on